Device for the continuous gravimetric metering and pneumatic conveying of pourable material

ABSTRACT

Disclosed is a device for the continuous gravimetric metering and pneumatic conveying of pourable material which is conveyed across a given distance by a metering rotor ( 1 ) which is arranged in a pressure-proof manner in a housing ( 2 ) and is provided with conveying pockets ( 1   a ). Said housing ( 2 ) comprises a charging station and a discharging station for the pourable material, which are connected to the inlet/outlet ( 4, 5 ) of a pneumatic conveyor system. The housing ( 2 ) is connected to a force metering device which detects the momentary load generated on the metering rotor ( 1 ) by the conveyed material. The inlet and outlet of the pneumatic conveyor system are connected to the bottom of the housing ( 2 ). In order to build the inventive device in a compact manner while reducing the assembly requirements and improving flow guidance, the flow from the inlet ( 4 ) to the outlet ( 5 ) is deflected within the upper area of the housing ( 2 ).

The present invention relates to a device for continuous gravimetricmetering and pneumatic conveying of pourable material, which isconducted over a measuring length using a metering rotor positionedpressure-tight in a housing and provided with conveyor pockets, thehousing having a pourable material delivery station and an emptyingstation having connections to lines of a pneumatic conveyor system andbeing connected to a force measurement device, via which the torque loadexerted on the metering rotor by the material conveyed is determined.

A device of this type is known as a metering rotor scale from U.S. Pat.No. 4,682,915 of the present applicant. In this case, a pneumaticconveyor system is provided for “blowing out” the conveyor pockets ofthe metering rotor, the feed line being guided from below to themetering rotor in order to blow out the pourable material upward fromthe conveyor pockets to the removal line and convey it further. Thisdevice has proven itself in principle. Since the compensators in thefeed and removal lines and in the pourable material delivery station,which are necessary for decoupling, are positioned on a line with thepivot axis of the metering rotor, construction problems may occur,however, in order to house these compensators above the metering rotor.The pourable material funnel on the delivery station is thus generallyoffset upward in order to guide the removal line of the pneumaticconveyor system further upward without a large deflection. In addition,a minimum air velocity must be maintained to blow through from bottom totop, in order to ensure the required discharge under all conditions.However, in the event of low conveyance quantities, this may lead todisproportionate quantities of air of the pneumatic conveyor system.

The present invention is thus based on the object of improving a deviceaccording to the features according to the preamble in regard toconstruction and installation complexity and flow guiding.

This object is achieved by a device according to the features of Claim1. Preferred embodiments are the object of the subclaims.

Through the flow reversal of the pneumatic conveyor system within thehousing, the line arrangement of the pneumatic conveyor system may besimplified and designed compactly. Thus, the two compensators of thefeed line and the removal line may be positioned outside the supportframe of the metering rotor scale, so that the tight construction spaceabove the metering rotor may be used better, for example, by a pourablematerial funnel which is placed lower or a smaller overall height of thesupport frame. In addition, the installation and possible necessarymaintenance or checking of the pneumatic conveyor system is made easierin this way through the better accessibility to the components. Theimproved flow guiding in the conveyor pockets of the metering rotor isespecially advantageous in this case, since the feed air guiding withinthe housing is reversed in its upper region directly above the meteringrotor and is directed from above through the conveyor pockets, so thatthe discharge of the pourable product is also supported through gravity.In addition, improved discharge out of the conveyor pockets and transferinto the removal line results, particularly for small conveyedquantities, through the eddying during the air reversal. Furthermore,the energy required for the pneumatic conveyor system is reduced, sincesmaller quantities of air and/or lower air velocities of the conveyingair are to be provided. Furthermore, the installation complexity isreduced since the flow reversal elements are integrated in the housingand no longer need to be mounted and/or sealed separately.

In the following, an exemplary embodiment of the device will bedescribed in greater detail on the basis of the drawing.

FIG. 1 shows a schematic cross-section of a metering rotor scale forbasic explanation of the construction principle;

FIG. 2 shows a side view of a metering rotor scale according to therelated art; and

FIG. 3 shows an enlarged illustration of one-half of the metering rotorscale having the design of the arrangement of the lines according to thepresent invention.

A metering rotor scale is shown in cross-section in FIG. 1. Thisessentially includes a housing 2 having a metering rotor 1, which hasmultiple conveyor pockets 1 a, rotating between sealing plates therein.The metering rotor 1 is driven by a controllable motor M. The conveyorpockets 1 a are positioned in the form of concentric rings in themetering rotor 1. In addition, openings (8; cf. FIG. 3) are providedradially on the inside, which are used in the related art to generateblocking air. A pneumatic conveyor system having feed and removal linesis connected to housing 2, in order to thus form an emptying station.Furthermore, a pourable material delivery station 14 (cf. FIG. 2) isimplemented above the housing 2, the housing 2 being mounted so it ispivotable around a horizontal axis, in order to act on a forcemeasurement cell 6 via a suspension 7 at a distance therefrom (cf. FIG.2). Because of the pivoting around the pivot axis A—A, shown in FIG. 2and formed by bearing 13 (cf. also FIG. 3), the torque load which isexerted by the material conveyed on the metering rotor 1 as themeasuring length is thus detected. Compensators, which are positionedtogether with the compensator 11 at the pourable material deliverystation on the pivot axis A—A, are provided for decoupling forceinfluences.

The suggested guiding of the pneumatic conveyor system 3 according tothe present invention is shown in FIG. 3. In this case, both connections4 a, 5 a of the feed line 4 and the removal line 5, respectively, of thepneumatic conveyor system 3 are connected to the bottom of the housing2. The feed line 4 leads to radially internal openings 8 in the meteringrotor 1 in this case, in order to be guided directly over them withinthe housing 2 in a deflection curve 2 c back downward to the conveyorpockets. The top 2 a of the housing 2 is sealed by a simple sealingplate 2 b, in contrast to the earlier construction.

Through this flow deflection and/or reversal within the housing 2, thedischarge out of the conveyor pockets 1 a is significantly improved,since even at low air velocities, vortexes arise which make thedischarge of the pourable material out of the conveyor pockets 1 aeasier and, in particular, gravity also acts on the pourable materiallocated in the conveyor pockets 1 a. Therefore, the discharge may beperformed reliably via the collection funnel 9 located underneath andthe removal line 5. The connection 5 a is implemented as a doubleconnecting piece in this case and is used, like the collecting funnel 9,for continuous transfer of the sector cross-section of the conveyorpockets 1 a to the tubular cross-section of the removal line 5.

The removal line 5 and the feed line 4 of the pneumatic conveyor system3 are preferably connected laterally to one another in this case via aclamp 10 on the support stand, so that the installation complexity isreduced. This is correspondingly true for the attachment of thecompensators 11 of the feed line 4 and the removal line 5 on a sharedbracket 12, so that the mounting complexity for the requiredcompensators 11 is also reduced here, since they may form oneinstallation unit. Therefore, the maintenance outlay possibly requiredin long-term use is reduced, since the compensators 11 are positioned sothey are easily accessible.

1. A device for continuous gravimetric metering and pneumatic conveyingof pourable material, which is guided using a metering rotor, positionedpressure-tight in an enclosed housing and provided with conveyorpockets, over a measuring length, the housing having a pourable materialdelivery station and an emptying station having respective connectionsto feed/removal lines of a pneumatic conveyor system and being connectedto a force measurement device, via which the torque load exerted on themetering rotor by the material conveyed may be determined, and the feedline and removal line of the pneumatic conveyor system being connectedto the bottom of the housing, wherein a flow deflector from the feedline to the removal line is positioned inside the upper region of thehousing.
 2. The device according to claim 1, wherein the feed line ofthe pneumatic conveyor system is connected to radially internal openingsin the metering rotor.
 3. The device according to claim 2, wherein theopenings are implemented in the form of shafts, which are positionedconcentrically to one another.
 4. The device according to claim 1,wherein the housing is closed on top by a sealing plate.
 5. The deviceaccording to claim 1, wherein the flow deflection inside the housing isimplemented at the emptying station in the form of a deflection curve.6. The device according to claim 1, wherein the conveyor pockets of themetering rotor are positioned concentrically to one another.
 7. Thedevice according to claim 6, wherein a collection funnel, fortransferring the cross-section of the conveyor pockets to the tubularcross-section of the removal line, is implemented on the bottom of thehousing.
 8. The device according to claim 1, wherein the connection ofthe removal line is implemented as a double connecting piece.
 9. Thedevice according to claim 1, wherein the feed line and the removal lineare connected to one another laterally from the housing by a clamp. 10.The device according to claim 1, wherein compensators of the feed lineand the removal line are attached to a shared bracket laterally from thehousing.